After more than half a century of development of epoxy copper clad laminate (CCL), the worldwide annual output of epoxy CCL is more than 300 million square meters. Epoxy CCL has been widely used as a reinforcement material for making epoxy printed circuit board (PCB). Epoxy CCL can generally provide desirable properties such as turn-on interconnection, insulation and support for circuits. In general, the properties of epoxy CCL can affect the signal transmission speed, energy loss, impedance, and the like of the PCB. Therefore, the performance, quality, processability, the manufacturing level, manufacturing costs, as well as long-term reliability and stability of the epoxy printed circuit board depend to a large extent on the properties of the CCL material.
Whether it is a lead-free CCL, high density interconnect (HDI) CCL, integrated circuit (IC) packaging reinforcements or high-performance flexible CCL, the CCL should have a good adhesive strength, excellent insulation properties, high heat resistance and humidity resistant. In some embodiments, inorganic filler are added to varnishes comprising epoxy resins to reduce costs and improve the performance of the epoxy CCL. Choice of which have a relatively large number of talcum powder, aluminum hydroxide, silica, mica, and so on, all the materials can be in the dimensional stability of the CCL, the direction of the thickness of the expansion coefficient (Z-CTE) to achieve significant results.
When the peel strength is low, there is a possibility that circuit peeling during the manufacturing process of a printed circuit board and the falling-off of mounted parts in the outermost layer may occur and this is undesirable.
Therefore, there is a need for metal clad laminates with improved peel strength. There is also a need for metal clad laminates with improved Z-CTE.